Owing to ever-increasing demands on the purity of exhaust-gas released from motor vehicles, methods are sought to reduce the formation of emissions during the combustion of fuel within the engine, and to chemically or physically convert emissions formed into more inert substances. In particular, a reduction in the emissions of nitrogen oxides, commonly referred to as NOx for short, is sought. In the case of large engines such as diesel engines, it is known to admix water as vapor or as a spray mist into the combustion air of the engine. However, this approach is scarcely used in motor vehicles and has been realized only occasionally in heavy goods vehicles. In particular, in the case of passenger motor vehicles, the reduction in the emissions of NOx through the admixing of water into the combustion air is not presently used because such measures are often associated with considerable additional outlay for the storage of water, which has a disadvantage in that the water must be replenished at regular intervals. Moreover, disadvantages arise in that the water carried onboard in this way can freeze at low ambient temperatures.
The inventors have recognized issues with such approaches and herein describe a recirculation device for an internal combustion engine that is configured to recirculate a portion of exhaust-gas through a recirculation device and into an air feed line coupled to the exhaust line. Moreover, according to the present disclosure, the recirculation device further includes a condensate collecting device that is designed to collect condensate out of the exhaust-gas stream cooled in the cooling unit and to conduct said condensate to the air feed line wherein an injection device may be included for injecting the condensate into the combustion air. As such, the air feed line, which may be designed to draw in combustion air and conduct the air to the engine, may be admixed with the injected condensate. Furthermore, the exhaust line that is designed to discharge an exhaust-gas stream from the engine may also include a cooling unit that is included to cool the exhaust-gas stream flowing therethrough in order to induce the generation of condensate formation.
In one example, a system and methods is based upon the insight that the engine exhaust gas comprises a high fraction of water vapor. In this way, the technical result is achieved that the high fraction of water vapor within the exhaust gas may be further used for the reduction of NOx emissions by injecting the condensed water into the combustion air of the engine in order to lower a combustion temperature within the engine. As such, systems and methods are conceived of wherein the NOx emissions may be reduced without using a user-refillable water tank, which thereby reduces space requirements on-board a vehicle, and also reduces a vehicle weight and operating complexities for the driver. Furthermore, a method according to the present disclosure eliminates problems with regard to the freezing of the water store carried onboard the vehicle.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings. It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.